What is the Customary System of Measurement?
A comprehensive history of the use of the customary system in the United States, what the units are, and how to use and convert them
Author
Tess Loucka
Published:
Oct 2024
Key takeaways
- • The customary system has been used in the US since before the American Revolution and is a by-product of the old British imperial system.
- • There is a wide range of units used in the customary system, unlike the units used in the metric system which are all based on the meter, gram, or liter, and are fractions and multiples of 10.
- • Customary system units include miles, yards, feet, inches, tons, pounds, ounces, gallons, quarts, pints, cups, fluid ounces, tablespoons, and teaspoons.
The United States is one of only three countries in the world that use the customary system of measurement. While everyone else is using the metric system and has been for hundreds of years, the US continues to use it, but why?
The US has been using the customary system since it gained its independence from Britain! The customary system is a by-product of the British imperial system used in Britain at the time.
As international trade became more popular in the 1700s, governments worldwide began advocating for a unified system of measurement. The metric system, created by the French, became this unified system.
Thomas Jefferson, the Secretary of State of the United States at the time, was interested in this system and reached out to French scientists asking for more information. However, when the French sent a ship to the United States carrying a one-kilogram weight and instructions on how the metric system worked, a giant storm passed through the Atlantic and blew the ship off course!
The ship never made it to the United States and the metric system didn’t either.
Of course, there have been many opportunities since then for the US to adopt the metric system, but US officials have always felt that switching systems would cause too much disruption to production.
Besides that, some believe that using the customary system sets the US apart as a leader rather than a follower.
Today, the United States teaches the metric system in schools so that students have an understanding of worldwide measurements, but in general use, the customary system is more common.
So, now that you know the history behind this system of measurement, let’s talk about how it works!
What is the customary system?
The customary system is the American system of measurement based on the imperial system. This system of measurement can be traced back to the Ancient Romans, Carolingians, and Saxons. It has a rich history and continues to be used throughout the country today.
Customary system vs metric system
As previously mentioned, the customary system and the metric system are the common systems of measurement.
The metric system uses the number 10. It is called a decimal-based system because to convert any unit to another, you either multiply or divide by 10.
In this way, the metric system is very straightforward. Besides being used as the official measuring system in most parts of the world, the metric system is also an International System of Units, or SI, and is commonly used in the world of science.
The metric system uses the meter (m) for distance or length, the gram (g) for mass and weight, and the liter (l) for volume and capacity. Very small or very large measurements use multiples or factors of these units.
The customary system, on the other hand, has a much wider variety of units. It is not a decimal-based system and does not use multiples of 10. In this way, measurements using the customary system can be a bit harder to understand.
So, let’s go over each of the customary units and put things into perspective.
Customary units of measurement
Measuring things with US customary units is easy once you know how the units work! Let’s start with the customary units of length.
Customary Units of Length
To measure length or distance, the customary system uses the mile (mi), yard (yd), foot (ft), and inch (in).
The mile is the largest unit used for length. When measuring the distance between two cities or how long your commute to school is, you use miles.
Yards are used to measure things like the size of rooms, the length of a field, or well, your backyard! It is much smaller than a mile, but can still be used for big measurements.
The foot is used to measure things like height or the length of furniture.
The inch is the smallest unit of distance measurement and is used for little things like measuring a pencil, a computer mouse, or your hand.
Customary Units of Weight
To measure weight, the customary units of measurement are the ton (tn), pound (lb), and ounce (oz).
The ton is the largest unit of weight measurement. You use this unit for big things like weighing a truck, a building, or even the Earth!
You use pounds to measure your own weight or the weight of furniture in your house. Weights at the gym are measured in pounds, too.
Ounces are the smallest unit of weight measurement and are used for measuring little things like kittens, babies, or food.
Customary Units of Capacity
Volume is measured in the customary system using the gallon (gal), quart (qt), pint (pt), cup (c), and fluid ounce (fl oz).
Gallons are used for measuring jugs of milk, bathtub capacity, and even larger things like swimming pools and even oceans!
Quarts are used for measuring slightly smaller quantities, like a carton of orange juice or the capacity of a watering can.
Pints are slightly smaller than quarts. Think of the cartons of milk you get at school. Those cartons hold about a pint of milk.
Cups are most commonly used when baking. Almost every baking recipe will call for a cup of flour, two cups of milk, ½ a cup of sugar, or some other fraction or multiple of a cup.
Lastly, the fluid ounce is used for measuring very small quantities of liquid. This unit can be found on the sides of bottles or cans of soda. Fluid ounces are also common units used in cooking and baking.
Tablespoons and teaspoons are other units for measuring capacity. These are the smallest units and are also mainly used when cooking or baking.
Examples of Customary System Units
As you can see, there are a lot of customary units of measurement! To better understand how these units work, you should take a look at how one unit can be converted into another.
Customary units of length conversion chart:
1 foot = 12 inches
1 yard = 3 feet
1 mile = 5,280 feet
1 mile = 1,760 yards
Customary units of weight conversion chart:
1 pound = 16 ounces
1 ton = 2,000 pounds
Customary units of capacity conversion chart:
1 tablespoon = 3 teaspoons
1 fluid ounce = 2 tablespoons
1 cup = 8 fluid ounces
1 pint = 2 cups
1 quart = 2 pints
1 gallon = 4 quarts
For more information on unit conversion and the customary system, visit a certified math website or math app. A dependable math resource can help you gain a greater understanding of math topics and build a foundation for further learning.
Practice Problems
Click on the boxes below to see the answers!
Answer: The dining table is 7.5 feet long. It is 90 inches long.
For this problem, convert yards to feet, then convert feet to inches. We know that 3 feet fit into 1 yard, so multiply 2.5 yards by 3 to get 7.5 feet. We also know that there are 12 inches in 1 foot, so multiply 7.5 feet by 12 to get 90 inches.
Answer: 6.5 tons
Convert pounds to tons. There are 2,000 pounds in 1 ton, so divide 13,000 pounds by 2,000 to get 6.5 tons.
Answer: 8 pints are needed
First, ¾ of 12 is 9. There are currently 9 gallons of water in the bucket. The bucket needs 3 more gallons of water until it is full. Next, convert gallons to pints. In 1 quart, there are 2 pints. In 1 gallon, there are 4 quarts. Multiply 2 pints by 4 to get 8 pints. There are 8 pints in 1 gallon. So, in 3 gallons there are 24 pints.
FAQs about the customary system
The imperial system is occasionally used in the United Kingdom. The United States commonly uses the customary system. Both systems use similar units of measurement, however, their units for volume are different.
The US has used the customary system since gaining its independence from Britain. The US has chosen to keep using the customary system because switching systems would likely cause too much disturbance to production and manufacturing in the country.
The metric system is a decimal-based system and uses fractions and multiples of 10. It is used in most countries. The customary system uses a wide range of units and is used in the United States, Myanmar, and Liberia.
